Most songs feature Wolf's original audio recordings.
You will need either Windows Media Player or RealOne Player to listen to the recordings.
A free version of RealOne player is available for download
here.

If clicking on the link takes you to a new window from which you cannot see the
lyrics while the song plays, right-click on the link instead of left-clicking,
and then select "Open in new window" from the drop-down box. Then you can
minimize that window and read the lyrics at the same time as the music plays.